Though its origins stretch back in Western thought, conservatism, as an organized set of ideas in the United States, can be said to begin when America's founding principles first were seriously challenged and in need of conserving. In the early 20th century a philosophical movement called Progressivism began to dominate mainstream American politics and academia. Progressives rejected the principles of the Founders and advocated reforming the American government as a centralized, administrative state. As Progressivism became increasingly prevalent, prominent political figures and intellectuals, including Calvin Coolidge, began to openly oppose the movement, advocating instead to maintain America's founding principles. As the 20th century progressed, Progressivism and subsequently liberalism would increasingly undermine and attack America's first principles. As these attacks grew stronger, so too conservatism grew stronger and became more visible. The conservative movement became particularly visible and more formalized after 1945 thanks to the energizing work of conservative intellectuals and politicians such as William F. Buckley Jr., Russell Kirk, and Barry Goldwater.